The objective of this investigation is to determine if the replication of Herpes simplex virus type 1(HSV-1) in vitro is inhibited by the substance known as 6-diazo-5-oxo-L-norleucine (DON) and specifically what the mechanism of inhibition is. Herpes simplex viruses cause orofacial and genital infections of humans and are the second most common cause of sexually transmitted disease. At the present time, acyclovir is only licensed prescription drug available for the treatment of HSV infections. Treatment of HSV infections with DON may prove to be an effective alternate therapy since some isolates are resistant to acyclovir. DON is an analogue of glutamine and as such inhibits the transfer of the amino group from glutamine to glucose, for the synthesis of glucosamine, and to nucleotide precursors for the synthesis of deoxyribonucleotides. Glucosamine is necessary for the synthesis of glycoproteins, and deoxyribonucleotides are necessary for the synthesis of DNA. Without glucosamine, enveloped viruses, like HSV, which are produced are not infectious and without deoxyribonucleotides, viral DNA synthesis is inhibited. Human epithelial (HEp-2) cells will be treated with DON prior to infection with HSV-1 to determine whether or not DON inhibits viral replication. If DON inhibits viral replication, experiments will be performed to determine if DON inactivates HSV-1 particles or interferes with viral adsorption to treated cells. DON is an analogue of glutamine and the addition of glutamine to medium containing DON prior to virus infection may reverse the inhibitory effects on viral replication. To determine if DON is affecting viral glycoprotein synthesis, viral DNA synthesis, or both, radioactively labeled glucosamine and thymidine will be added to DON treated, virus infected cells 4 hours post infection when host cell protein and DNA synthesis have been inhibited by the HSV-1 infection process. The addition of glucosamine and/or deoxyribonucleotides to DON treated HEp-2 cells prior to infection may specifically reverse the metabolic inhibition caused by DON and allow HSV-1 to replicate even in the presence of DON. Finally, HSV-1 particles produced in the presence of DON, if any, will be used to infect DON treated cells to determine if a population of viruses resistant to DON may arise. If successful, these experiments may lead to the clinical evaluation of the effectiveness of DON as a treatment for HSV infections.